Note that although the present invention relates generally to acoustic waves and to acoustic wave receivers/transducers, for clarity we will refer to the most common examples, namely sound waves and microphones. Some classes of microphone transducer technologies which are known to the audio community are: carbon, condenser, moving-coil (or "dynamic") and piezoelectric. Using these technologies microphones with varying sensitivity to direction, proximity, impedance and frequency can be constructed. Some of these are: cardioid, pressure gradient, and microphone array. The existing background literature in this field is extensive, however, some very good technology reviews are described in references: L. Beranek, Acoustics, American Institute of Physics, New York, N.Y., 1986; and L. E. Kinsler, Fundamentals of Acoustics, John Wiley & Sons, Inc., New York, N.Y., 1982. In addition, microphone manufacturers (for example B&K Shure and Electrovoice) have application notes and product literature which describe the performance of these devices.
Indeed, the review articles and the current literature describe a need for microphone systems which have increasingly larger signal to noise ratio, and increasingly larger directional sensitivity (i.e., increased sensitivity to acoustic waves originating from a particular direction). While the devices described above address these needs to some degree, problems still exist. For example, current state-of-the-art microphones with relatively high signal to noise ratios tend to be sufficiently large to scatter the waves, thus affecting the received sound waves. This is problematic as it both distorts the signal produced by the microphone, as well as changes the waves for subsequent receivers or listeners.
Other background information which may be useful in understanding the invention and the techniques described herein is found in: Horowitz and Hill, The Art of Electronics, McGraw-Hill; S. W. Golomb, Shift Register Sequences, Aegean Park Press, 1982; and G. Arfken, Mathematical Methods for Physicists, Academic Press, Inc., New York, N.Y., 1985, which are all hereby incorporated by reference.